A banyan tree, perhaps?

Though I'd even problematise the idea of a main trunk.

'Core' is also a problem for me as interesting stuff is more likely to be happening at the margins.

But whatever is wrong with 'large, contains multitudes, contradicts itself'? I am resistant to definitions of The Real True Whatever and the One True Way:

There are nine and sixty ways of constructing tribal lays,
And every single one of them is right!